Dr. Peter Pronovost, one of the nation’s top patient safety experts and advocates, is leaving Johns Hopkins Health System for a job at insurance giant UnitedHealthcare, he announced Thursday on Twitter.

“A great opportunity to help improve care for millions,” tweeted Pronovost, currently Hopkins’ senior vice president for patient safety and quality and director of the Armstrong Institute for Patient Safety and Quality.

Pronovost did not respond to a request for comment about his planned mid-January move.

Patients at Johns Hopkins hospitals and most other health care facilities around the country may not know his name, but if their surgery went smoothly or they left the ICU without an infection they may have Pronovost to thank. He’s known for developing checklists and pushing large health systems to adopt them.

His push to improve clinical care required a cultural change among medical providers and might have rankled some.

But it was effective. For example, after he was named to head the Armstrong Institute in 2011, he took on the bloodstream infections that often developed through the main catheters used to deliver medicine and fluids to patients. New protocols developed, including simple methods to keep them clean, led to an 80 percent drop in such central-line-associated infections.

Hopkins research suggests that medical errors are the third leading cause of death in the United States. The 250,000 deaths annually make errors less deadly than only heart disease and cancer and more fatal than respiratory disease. The researchers called for more preventive work and better tracking of the problem, still largely out of the public eye.

In an email blast to the Hopkins community, leadership at Hopkins Medicine said there will be a search for his successor and interim measures will be announced shortly.

“A practicing critical care physician, Peter has devoted his career to making hospitals and health care safer,” said the email “Beyond any question, under Peter’s stewardship the Armstrong Institute has emerged as a leader in helping to reduce errors, improve clinical outcomes and experiences, and reduce waste in health care delivery at Johns Hopkins and throughout the world.”

They note that Pronovost was named one of Time magazine’s 100 most influential people in the world and received the MacArthur Fellowship, known as the “genius grant” for the work at Armstrong.

In a statement welcoming Pronovost to UnitedHealthcare, the insurer said he “has distinguished himself nationally and internationally with his ground-breaking work around saving lives, improving patient safety, and improving both the quality and value of health care...

“Dr. Pronovost’s patient-centered approach to care and deep clinical expertise will help bring a provider point-of-view deeper into UnitedHealthcare and improve how payers and care providers work together to share best practices, build appropriate value-based incentives, and effectively use data to improve the patient experience.”

Dr. Albert Wu, a colleague who directs an Armstrong center focused on quality measures, called Pronovost a “revolutionary thinker” and his departure “a body blow,” though the Armstrong center will continue its work because Hopkins has a deep bench of talent.

“In some ways, virtually everyone who received medical care in the United States has benefited directly or indirectly from his work,” said Wu, an internist and Hopkins professor of health policy and management whose wife is a part-time editor at The Baltimore Sun. “He’s transformed thinking about what is possible. … Many harms were simply accepted as part of medicine. But it’s been demonstrated that it’s possible to achieve zero harm in a few limited places where there has been a great deal of light shined.”